The present invention relates generally to the field of waveguides and waveguide devices and, more particularly, to transitions from waveguide media to suspended substrate circuits. Still more specifically, the present invention relates to transitions from double-ridge waveguide to suspended substrate millimeter wave circuits.
Prior to this invention, transitions to suspended substrate were available over bandwidths corresponding to the lowest order waveguide mode or over bandwidths limited by higher order modes in coaxial transitions. With respect to waveguides, for example, transitions could be fabricated to cover 18-26.5 GHz and other transitions could be fabricated to cover the 26.5-40 GHz band. No transitions, however, could be built to cover, for example, the 20-40 GHz band.
Coaxial transitions covering up to 40 GHz have recently become available for use with microstrip circuits. They are, however, fragile and the circuits must be soldered to the center tabs of the coaxial connector. Further, these types of coaxial transitions have reached their limit in frequency scalability. Difficulties have been encountered with their use with millimeter wave suspended substrate circuits. Also, their small dimensions will limit their use at high power levels.